1 files changed, 65 insertions, 0 deletions
diff --git a/nearby/crypto/crypto_provider_openssl/src/hkdf_boringssl.rs b/nearby/crypto/crypto_provider_openssl/src/hkdf_boringssl.rs
new file mode 100644
index 0000000..63e0ebc
--- /dev/null
+++ b/nearby/crypto/crypto_provider_openssl/src/hkdf_boringssl.rs
@@ -0,0 +1,65 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! BoringSSL based HKDF implementation. Unfortunately, because the OpenSSL and BoringSSL APIs
+//! diverged for HKDF, we have to have separate implementations.
+//!
+//! See the _Using BoringSSL_ section in `nearby/scripts/prepare_boringssl.sh` for instructions on
+//! how to test against BoringSSL.
+
+use crate::OpenSslHash;
+use crypto_provider::hkdf::InvalidLength;
+use std::marker::PhantomData;
+
+/// openssl based hkdf implementation
+#[derive(Clone)]
+pub struct Hkdf<H: OpenSslHash> {
+    _marker: PhantomData<H>,
+    salt: Option<Vec<u8>>,
+    ikm: Vec<u8>,
+}
+
+impl<H: OpenSslHash> crypto_provider::hkdf::Hkdf for Hkdf<H> {
+    fn new(salt: Option<&[u8]>, ikm: &[u8]) -> Self {
+        Self {
+            _marker: Default::default(),
+            salt: salt.map(Vec::from),
+            ikm: Vec::from(ikm),
+        }
+    }
+
+    fn expand_multi_info(
+        &self,
+        info_components: &[&[u8]],
+        okm: &mut [u8],
+    ) -> Result<(), InvalidLength> {
+        // open ssl will panic in the case of a 0 length okm, but expected behavior is no-op
+        if okm.is_empty() {
+            return Ok(());
+        }
+        openssl::hkdf::hkdf(
+            okm,
+            H::get_md(),
+            self.ikm.as_slice(),
+            self.salt.as_deref().unwrap_or_default(),
+            &info_components.concat(),
+        )
+        .map_err(|_| InvalidLength)
+        .map(|_| ())
+    }
+
+    fn expand(&self, info: &[u8], okm: &mut [u8]) -> Result<(), InvalidLength> {
+        self.expand_multi_info(&[info], okm)
+    }
+}